Give the world creation tools and watch what happens. The best map editors around always see some of the more interesting creations come out of their fan base. Most of the time people do some pretty uninspired stuff (like the millions of recreations of Super Mario Bros. 1-1 in every game imaginable).
However, when people got their hands on Doom's new Snapmap mode it took a week or so but what they realized they could recreate eventually became much larger. Here's the beginning of someone working to remake an entire Destiny raid in Doom's snap map.
Right now they've only got the opening up. Like actually opening up the raid (because it wouldn't be Destiny if there wasn't a rather obtuse and unexplained beginning to the damn raid, but hey, that's half the charm).
A lot of logistical planning will have to go into this to further work and develop the entire raid in a different engine but Snapmap has proven pretty useful thus far. I'm really looking forward to seeing where this goes!